Textile fibers or filaments from synthetic polymers, particularly polyamide polymers like nylon 66 and nylon 6, and multi-filament yarns melt-extruded from the same polyamide polymers, are produced for many apparel uses. The most common cross-sectional (taken longitudinally to the long axis of the filament) shape for each filament comprising the multi-filament yarns is circular. However, many variations on the individual filament cross-sectional shapes exist. These include a “dogbone” cross-sectioned filament commercially available from E. I. DuPont de Nemours and Company of Wilmington, Del. USA and known as TACTEL® Diabolo. A bi-lobal filament cross-sectional shape is disclosed in U.S. Patent Application Number 2002-0034903-A1 (Shoemaker, et al.). Other known shapes include tri-lobed or even 6-lobed, disclosed in Japanese Kokoku patent document 01-20243 (Nihon Ester KK). Another multi-lobal cross-sectioned fiber, available from DuPont and known as Coolmax™, is shown in U.S. Pat. No. 5,152,014.
Filaments with cross-sectional shapes other than circular provide multi-filament yarns for fabrics and garments with varied visual aesthetics including those known in the art as glitter, sparkle, matt appearance, and increased opacity or cover. Lighter fabric weight and fabric flatness are also achieved through variations in the individual filament cross-sectional shape. Among these numerous profiled cross section fibers used in synthetic filaments for apparel, certain other cross sections have been developed to enhance the ability of filaments to absorb or wick moisture.
Moisture wicking, which refers to the capillary movement of water through or along the fibers, is considered a desirable feature in apparel fabrics as it improves comfort to the wearer by spreading moisture away from the skin so that it can evaporate more readily. In addition, combinations of cross-sections, denier per filament (dpf), and finish preparations applied to filaments and fabrics have been developed to enhance the ability of filaments to absorb or wick moisture. For example, “two-sided” fabrics have been developed to help move moisture from the inside to the outside of the fabric due to the surface chemistry. Typically, the two-sided fabrics have fine denier per filament (dpf) filaments primarily on the outside, and coarser dpf filaments primarily on the inside. Although this “two-sided” fabric is readily accomplished in weft knit fabrics through knitting construction, there is room for further improvement in wicking through optimum shape of the individual filaments. In addition, warp knit and woven fabrics are difficult and expensive to construct in a manner to maintain filament location primarily on one side or the other. Therefore, especially in wovens and warp knits, a filament that provides superior moisture wicking is needed to improve wearer comfort, especially for active wear.
There is a continuing need to provide multifilament synthetic yarns that provide enhanced moisture wicking properties to fabrics as well as a soft fabric hand and silk-like luster for apparel.